Highpressure behavior of TiO_{2} as determined by experiment and theory
Abstract
Using highresolution synchrotron xray powder diffraction we have investigated the structural phase transitions and equations of state of titanium dioxide (TiO_{2}) under high pressure before and after heating at high temperature. The phase sequence we observe experimentally is as follows: rutile (RT)→columbite(CB)→baddeleyite(MI)→orthorhombicI(OI)→orthorhombicII(OII) . The equations of state as determined from our experiments are consistent with previous measurements and computations. The only exception is the OII phase for which we find a significantly lower roompressure bulk modulus (K_{0}) of 312 (±34)GPa and roompressure volume (V_{0}) of 25.28 (±0.35)Å^{3} as compared to previous experiments. We find that the volume decreases across the OI→OII phase transition at room temperature by ̃8.3% , in very good agreement with our static firstprinciples calculations which predict volume changes of 8.2% and 7.6% for localdensity approximation and generalized gradient approximation, respectively. This volume collapse is significantly higher than previously determined but consistent with the volume decrease observed in other dioxides across this transition.
 Publication:

Physical Review B
 Pub Date:
 April 2009
 DOI:
 10.1103/PhysRevB.79.134114
 Bibcode:
 2009PhRvB..79m4114A
 Keywords:

 81.40.Vw;
 31.15.A;
 64.70.K;
 61.50.Ks;
 Pressure treatment;
 Ab initio calculations;
 Solidsolid transitions;
 Crystallographic aspects of phase transformations;
 pressure effects